This invention relates to an electrically operated military target capable of emitting an infrared signal when an electrical current is passed therethrough. The target also presents a visual image when exposed to visible light, said visual image being detectable and identifiable with the unaided eye, or when using a wide range of optical lenses and electrooptical viewing systems including image intensification equipment.
With the advent of thermal sights for conducting military operations such as surveillance, reconnaissance, target detection and tracking, and weapon system guidance, there arose a need for targets suitable for conducting training in these military skills. Infrared detection and sighting equipment is now available in a large number of configurations, levels of capability and technical sophistication and is depolyed on a wide variety of military platforms. These include strike and reconnaissance aircraft, helicopters, ships of various types, and many armored fighting vehicles--(AFV's)--such as main battle tanks (MBT's), armored personnel carriers (APC's) and numerous other general and special purpose vehicles. Infrared detection devices have even been made small enough to be manportable.
The use of infrared detection and sighting equipment for military applications is expanding due to the potential such equipment possesses to improve the combat effectiveness of military forces, especially at night, in adverse weather, and in some conditions of obscured visibility, such as when a battlefield is visually obscured by smoke from fires, smoke canisters or generators, or other pyrotechnics. Acquisition of the ability to conduct operations at night, however, through the use of infrared detection and sighting equipment is a particularly significant factor motivating many of the world's armed forces to develop and depoly such equipment in large numbers, and to constantly upgrade existing systems. Such equipment has already been proven effective in combat.
The effectiveness of infrared detection and sighting equipment is due to the fact that all objects possessing a surface temperature greater than absolute zero dissipate energy in accordance with the laws of thermodynamics. One principal way in which that energy is dissipated is through the process of radiation, where the energy is emitted in the form of an electromagnetic transmission having wave lengths and amplitudes determined by the object's surface temperature. This dissipated heat energy traveling through air or space is known as infrared radiation, and infrared detection and sighting devices can sense these transmissions. The equations, physical laws and constants necessary to calculate the specific characteristics of such infrared, or IR, radiation and the reference sources that can be useful to assist such work are well-known.
IR detection and sighting equipment, by sensing the IR radiation emitted by an object, can thus be said to be able to `see` that object by the heat it gives off as radiation. This detectable radiated heat energy, also known as thermal energy, is called the object's thermal signature, and an IR detection and/or sighting device that can `see` an object's thermal signature is also known as a thermal imager.
The ability to detect a military asset such as an enemy tank, plane or ship by the target's thermal signature is of military importance. Moreover, if the thermal signature is sufficiently strong and clear, it can be used to identify the target by its type and reveal certain information about its operating condition, such as whether it is moving, sitting with the engine idling, or a number of other things. Such thermal imaging techniques are well-known in the art.
In order to exploit the potential of these thermal imaging systems, the crews of planes, helicopters and AFV's equipped with such systems must be trained to be proficient in their use. This is true because the thermal signature of a military asset such as an enemy tank bears some, but not a total, resemblance to that asset's visual signature. Since it is the visual signature of the asset that such crew members have previously learned to see with their eyes, they must be taught to recognize the thermal signature of the same asset. This is not a simple recognition process to learn: the thermal signature of an asset not only differs from the visual signature, but can itself also vary, depending upon the operating condition of the asset and the state of its environment.
The required level of proficiency can only be achieved through detailed training, and a useful element in any thermal imager training program is a thermal target. A suitable target would be able to simulate the thermal signature of a military asset such as a tank or other vehicle. While a real vehicle would be the ideal target for such training, these are usually very expensive to use for weapon system live fire training, and in the case of most modern enemy equipment, typically not available at all.
It is desirable that the IR radiation emitted by the target simulate the radiation characeristically emitted by the real military asset as to both intensity and pattern. Each type of asset such as enemy equipment emits thermal energy in a manner dependent upon a number of factors. These factors include the type of equipment, whether it is operating or not, and the weather conditions prevalent at the time of observation. This characteristic thermal signature is composed of a number of key elements, known as thermal signature cues. The cues can be used by personnel proficient in the use of thermal imaging equipment not only to detect a target, but also to identify it by nationality and type of equipment, to determine whether the target is moving, and if so, in which direction, to determine if it is firing or has recently fired its weapons, and to ascertain many other items of militarily valuable information.
For example, a tank moving on a road will have its tracks quickly heated through friction with the road surface, and the tracks with heat the road wheels, drive wheels and idler wheel through conduction. These hot tracks and wheels emit IR radiation which is detectable by a thermal imager, and so the hot tracks and wheels form part of the tank's thermal signature. Because the tracks form large, intense and easily identifiable portions of that signature, and because the wheels provide round, easily identifiable elements in the same signature, the tracks and wheels of an enemy vehicle are important thermal signature cues. Under proper viewing conditions, proficient personnel can count wheels, gauge their diameter and spacing relative to the rest of the thermal signature, and use this information to identify the vehicle by type and nationality. If all the wheels are clearly identifiable, but the tracks are not, these facts can be used to determine that the vehicle is a tank viewed from a flank aspect. These are just some of the ways that the cues of a thermal signature can be interpreted to yield valuable information. Clearly, other types of equipment will have their own distinctive cues enabling them to be identified with a thermal imager.
A target that simulates the thermal cues of an enemy vehicle's thermal signature can be used for a number of training purposes, including:
1. Detection Training: where AFV crews would be taught to discriminate the thermal signature of an object from its background and assign this detected thermal signature to a class of potentially interesting (or threatening) objects. PA1 2. Classification Training: where the AFV crews would lean to assign the detected thermal signature to a gross class of objects (such as vehicles, or helicopters on the ground, etc.) PA1 3. Recognition Training: where the AFV crew learns to assign the classified object to a specific subclass such as tanks, or trucks. PA1 4. Identification Training: where the AFV crew learns to assign the recognized thermal signature to an even more specific category such as M-60 tanks, or 2.5 ton trucks.
Those expert in the field of training and target analysis will recognize that the degree of difficulty in accomplishing these tasks increases from detection to identification. A single target that is sufficiently accurate to permit any level of the above training would have real value, as it would allow AFV crews to learn as much as they could without having to change training devices.
These same values accrue if the target possesses an accurate visual signature of the enemy vehicle as well. Thus with one target, thermal and visual detection, classification, recognition, and identification training can be accomplished simultaneously. As an AFV crew would use thermal and visual sighting systems simultaneously in combat if possible, this permits the crew to exercise their equipment in training as they would use it in battle.
If the target not only has the thermal signature of a vehicle, but also the visual signature superimposed upon the thermal signature, it is known as a multi-spectral target. Being on the target face, the visual signature is unobscured, and the thermal signature can be radiated through the visual signature. From dawn to dusk, and in night situations where image intensification and electro-optical devices can be used, an enemy's visual signature can be used for detection purposes. Friendly personnel must be proficient in recognizing both the enemy's thermal and visual signatures, and thus a multi-spectral target is of great value.
Such a multi-spectral target can also be upgraded to provide a radar signature as well. This can be accomplished in a number of ways including the use of aluminum or other metallic foils bonded or otherwise attached to the target and formed as necessary to simulate the corners, crevices, joints and voids characteristic of the military asset being simulated. A preferred embodiment uses corner reflectors suitably sized and positioned and other metallic or conductive meshes and materials incorporated into the target, interconnected in a low impedance circuit, as necessary. Those familiar with milimeter wave and radar signature generation and detection will easily recognize the number of ways in which an acceptable radar signature can be simulated.
Multi-spectral targets that simulate the signatures of our own vehicles or those of our allies are also useful. Our personnel must be proficient in recognizing when not to shoot at a detected vehicle because it is a so-called `friendly` vehicle. This proficiency can be gained through `friend or foe` target recognition and identification training in which targets simulating both friendly and enemy vehicles are presented. Such training reduces the chance of fratricide during a confused combat situation.
Additionally, multi-spectral targets that effectively simulate our own vehicles can be used as decoys against an enemy in a battle. Since the targets accurately represent the detectable signatures of our vehicles and equipment, they are effective in a deception operation intended to confuse the enemy about the numbers, types and locations of our deployed forces. They draw his first away from our real equipment and divert his attention so that ambushes and other military maneuvers can be executed effectively.
The most useful embodiment of such a multi-spectral target is one which is easily carried into the field by the troops who will use it for training or other purposes. Such a target configuration should be very lightweight, so it is man-portable; of few parts, so it is easy and quick to set up and start operating; and reliable, so training or other missions can be executed faithfully and with confidence. The preferred multi-spectral target has its own support structure so that it can be set up anywhere, quickly, in response to any training or other military requirement. It should also be relatively inexpensive in order that it can be used for live fire training if necessary, or set up and expanded as part of a military deception operation.
Accordingly, there is a need in the art for a low cost expendable target for use in live fire or many other types of training and military purposes, which will emit thermal radiation that closely matches the thermal signatures of enemy or friendly assets as they appear in the field, and will reflect visible light in a manner so as to simulate the corresponding visual signature of that asset. Such a target should be self-contained, easy to transport, set up and use in the field, reliable, and durable enough to support a variety of military operations. Advantageously, it can be upgraded to include the corresponding radar frequency signature of that asset. Ideally, it should be repairable to promote its long term useful life.